Đáp án + Giải thích các bước giải:
$\text{a) x⁶ – 6x⁴ + 12x² – 8 = 0}$
⇔ $\text{(x² – 2)³ = 0}$
⇔ $\text{x² – 2 = 0}$
⇔ $\text{x² = 2}$
⇔ $\left[\begin{matrix}x=\sqrt[]{2}\\x=-\sqrt[]{2}\end{matrix}\right.$
$\text{Vậy x = $\sqrt[]{2}$; – $\sqrt[]{2}$}$
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$\text{b) (x – 9) (x – 7) = – 1}$
⇔ $\text{x² – 7x – 9x + 63 = – 1}$
⇔ $\text{x² – 16x + 63 = – 1}$
⇔ $\text{x² – 16x + 63 + 1 = 0}$
⇔ $\text{x² – 16x + 64 = 0}$
⇔ $\text{(x – 8)² = 0}$
⇔ $\text{x – 8 = 0}$
⇔ $\text{x = 8}$
$\text{Vậy x = 8}$
$\text{Xin hay nhất ạ!}$
$\text{@Sherry2007}$
